The present invention relates to the use of polyamino acid derivatives in a cosmetic composition to strengthen and care for keratin fibres, in particular the hair.
The present invention also relates to a xe2x80x9cdirectxe2x80x9d or xe2x80x9cin-situxe2x80x9d treatment process to strengthen and care for keratin fibres.
The expression xe2x80x9cdirect processxe2x80x9d means the treatment of the fibres by applying to them a cosmetic composition containing, in a cosmetically acceptable vehicle, at least one pre-synthesized polyamino acid derivative.
The expression xe2x80x9cin-situ processxe2x80x9d means the treatment of the fibres using precursors which generate a polyamino acid derivative in these fibres.
Different classes of polyamino acids have been described, and their use is well known and widely practised, in particular for their moisturizing properties.
In this respect, Japanese patent application JP-07/041 467 discloses a class of polyamino acids of high molecular weight consisting essentially of cysteine, as well as to the process for preparing these polyamino acids.
A class of polyamino acids characterized by the presence of thiol and/or disulphide functions has also been disclosed in Japanese patent application JP-06/248 072. These polyamino acids react with the thiol linkages of keratin, thus forming disulphide bridges, which makes it possible to increase the sheen and coloration qualities of the hair.
Another class of polyamino acids has been disclosed in Japanese patent application JP-04/198 114, these compounds consisting essentially of amino acids containing neutral and acidic chains, and are generally used as moisturizing agents.
Finally, French patent application FR-2 533 209 discloses amphipathic lipopeptides consisting of a hydrophilic peptide chain and a hydrophobic chain of 8 to 24 carbon atoms, as well as to their use as emulsifiers for immiscible media or for producing liquid crystals.
After numerous studies carried out on various classes of polyamino acids, it has been found, surprisingly and unexpectedly, that one particular class of polyamino acid derivatives has considerable properties in terms of strengthening keratin fibres, resulting from the formation of a substantial deposit of polypeptide material on the surface of the keratin fibres.
The use of these polyamino acid derivatives in cosmetic hair compositions moreover makes it possible to improve the hold and volume of the hair.
One subject of the present invention is thus the use, in a cosmetic composition for strengthening keratin fibres, of at least one polyamino acid derivative of general formula (I) below: 
in which:
X is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94NR3xe2x80x94
R1 represents:
(i) a hydrogen atom, and preferably
(ii) a linear or branched, saturated or unsaturated, C1-C40 alkyl radical, optionally substituted with at least one hydroxyl or a radical 
xe2x80x83and/or optionally interrupted with at least one hetero atom chosen from N, O or Si, rxe2x80x2 and rxe2x80x3, which may be identical or different, being a hydrogen atom or a C1-C6 alkyl radical, 
R2 represents a hydrogen atom or a C1-C8 alkyl, xe2x80x94CH2C6H5, xe2x80x94CH2C6H5pxe2x80x94OH, xe2x80x94CH2OH, xe2x80x94CHOHxe2x80x94CH3 or xe2x80x94(CH2)txe2x80x94NH2 radical, t being 3 to 5,
R3 represents a hydrogen atom or a C1-C6 alkyl radical,
R4 represents a hydrogen atom, xe2x80x94NH2, xe2x80x94OH, xe2x80x94SH, xe2x80x94CHOHCH3, xe2x80x94CONH2, 
xe2x80x83xe2x80x94C6H5 or xe2x80x94C6H5pxe2x80x94OH, and
n is an average number greater than 1 such that the molecular weight of the polyamino acid derivative is between 200 and 200,000, the repeating unit being either identical for the same derivative, or different, R2 and/or R3 then taking at least one of the other meanings given for these radicals,
or of a salt of the said polyamino acid derivative.
According to one preferred embodiment, the radical R1 is other than a hydrogen atom.
The polyamino acids of formula (I) are known in certain cases and novel in other cases.
The process for preparing them consists of a polycondensation reaction between at least one N-carboxyanhydride or formula: 
in which:
R2 and R3 have the same meanings as those given above for formula (I), and a nucleophilic compound of formula (III):
R1xe2x80x94XHxe2x80x83xe2x80x83(III)
xe2x80x83in which R1 and X have the same meanings as those given above for formula (I).
The N-carboxyanhydrides of formula (II) are prepared by the usual methods, by reacting a D and/or L-xcex1-amino acid with phosgene in an inert solvent such as dioxane or tetrahydrofuran (THF).
The polycondensation reaction is generally carried out at a temperature of between about 0xc2x0 C. and 120xc2x0 C. in an inert solvent chosen from benzene, toluene, chlorobenzene, dichloroethane, dimethylacetamide (DMAC), dimethylformamide (DMF), methyl ethyl ketone (MEK), aliphatic ethers such as ethyl ether, isopropyl ether and tert-butyl methyl ether, and cyclic ethers such as tetrahydrofuran and dioxane. However, the reaction solvent can optionally be water.
The formation of a more or less pronounced evolution of CO2 can be observed from the start of the reaction.
After optionally cooling the reaction medium, the solvent is evaporated off and the polyamino acid derivative obtained is then dried under vacuum.
Depending on the purity obtained, a purification step such as a precipitation or a crystallization of the crude product obtained can be carried out.
In the process for preparing the polyamino acid derivative as described above, the nucleophilic compound acts as an initiator for the polycondensation reaction.
According to one preferred embodiment, the molar amount of the nucleophilic compound of formula (III) is xc2xd-{fraction (1/3000)}, preferably ⅕-{fraction (1/2000)} per mole of the N-carboxyanhydride of formula (II).
Among the N-carboxyanhydrides of formula (II) which may be mentioned in particular are:
glycine N-carboxyanhydride,
sarcosine N-carboxyanhydride,
threonine N-carboxyanhydride,
serine N-carboxyanhydride,
valine N-carboxyanhydride,
norvaline N-carboxyanhydride,
isoleucine N-carboxyanhydride,
leucine N-carboxyanhydride,
norleucine N-carboxyanhydride,
lysine N-carboxyanhydride,
phenylalanine N-carboxyanhydride,
tyrosine N-carboxyanhydride, and
the above N-carboxyanhydrides optionally in protected form.
Among the nucleophilic compounds of formula (III) which may be mentioned in particular are amines such as 2-aminoactadecane-1,3-diol, 2-octyldodecylamine, hexylamine, oleylamine, glucamine, lysine, arginine, histidine and glutamine, alcohols in alkoxide form such as sodium methoxide, and thiols such as cysteine.
The compositions according to the invention can be in various forms and can contain the polyamino acid derivative in a proportion generally of between 0.001% and 30% and preferably between 0.01% and 15% by weight relative to the total weight of the composition.
According to a first embodiment of the compositions according to the invention, they are in the form of a shampoo or a pre- or post-shampoo care composition for strengthening keratin fibres.
The cosmetically acceptable vehicle for these compositions is either an aqueous medium or an aqueous-alcoholic medium containing an alcohol such as ethanol or isopropanol.
The compositions in the form of a shampoo also contain at least one anionic, nonionic, zwitterionic, amphoteric or cationic surfactant.
The proportion of surfactant is generally between 0.01% and 50% by weight, but preferably between 0.05% and 30% by weight, relative to the total weight of the composition.
When a surfactant of the nonionic type is used, it is generally used in a proportion of between 0.1% and 40% by weight, and preferably between 1% and 20% by weight, relative to the total weight of the composition.
On account of the weaker detergent power of the surfactants of cationic type, they are used more particularly in the pre- or post-shampoo care compositions.
The surfactants which can be used in the compositions according to this embodiment are well known in the prior art and have been described in particular in patent FR-2 728 163.
These pre- or post-shampoo care compositions can also contain a conditioner.
As conditioners which can be used in the compositions according to the invention, mention may be made in particular of hydrogenated or non-hydrogenated natural oils, saturated or unsaturated, linear or branched, cyclic or aliphatic, hydrocarbon-based synthetic oils such as, for example, poly-xcex1-olefins, in particular polydecenes and polyisobutenes, soluble or insoluble, organomodified or otherwise, volatile or non-volatile silicone oils, fluoro oils, perfluoro oils, fatty esters, esters of polyhydric alcohols and glycerides.
Synthetic or natural waxes, silicone gums and resins, quaternized or non-quaternized proteins or protein hydrolysates or a mixture of these various agents can also be used as conditioners.
The compositions according to this first embodiment can also contain at least one cosmetically or dermatologically acceptable additive chosen from a thickener, a polymer of cationic, anionic, nonionic or amphoteric type, a sunscreen, a ceramide, an xcex1-hydroxy acid, a preserving agent, an antimicrobial agent, an anti-dandruff agent, a pearlescent agent, a dye, a fragrance, an electrolyte or a suspension agent.
The additives are generally present in the compositions according to the invention in a proportion of between 0.01% and 20% by weight, and preferably between 0.02% and 10% by weight, relative to the total weight of the composition.
The pH of the compositions according to the invention is generally less than 7 and preferably between 3 and 4.5.
According to a second embodiment of the compositions according to the invention, they are in the form of a composition for forming a mousse of anhydrous or aqueous type.
When the mousse composition is of anhydrous type, it comprises a fatty phase as cosmetically acceptable vehicle, a foaming agent and a propellant.
Among the oils and waxes which can be used, mentioned may be made in particular of those of plant, animal, mineral or synthetic origin. These oils and waxes are well known in the prior art and are described in particular in patent FR-2 668 927.
The cosmetic oil or the mixture of oil and wax is generally present in a proportion of between 20% and 99% by weight, but preferably between 25% and 85% by weight, relative to the total weight of the fatty phase.
When the mousse composition is of aqueous type, it comprises an aqueous solution or an aqueous-alcoholic mixture as cosmetically acceptable vehicle, a foaming agent and a propellant.
The aqueous-alcoholic mixture can contain, for example, a C1-C4 alcohol such as ethanol or isopropanol.
When an aqueous-alcoholic solution is used, the proportion of alcohol does not exceed about 50% and is preferably less than 30% by weight relative to the total weight of the composition.
Among the foaming agents or surfactants which can be used, mention may be made, inter alia, of anionic, nonionic, zwitterionic, amphoteric and cationic surfactants. Mention may also be made of cationic or anionic polymers such as those described in patent application FR-82/07996, or alternatively the combination of cationic and amphoteric polymers as described in patent application FR-96/02125.
The proportion of foaming agent can be between 0.05% and 20% by weight, preferably between 0.2% and 10% by weight and more particularly between 0.25% and 5% by weight, relative to the total weight of the composition.
The mousse compositions of aqueous type can also contain a plasticizer in a proportion of between 0.01% and 16% by weight relative to the total weight of the composition.
The plasticizers which can be used are well known and are described in particular in patent FR-2 719 995.
Among the ingredients which can be added to the mousse compositions, mention may be made of dyes, whose function is to colour the composition itself or the hair, preserving agents, sequestering agents, pH regulators, fragrances, vitamins, plant and animal extracts, silicones, sunscreens and other agents for treating keratin fibres.
Among the propellants preferably used in these mousse compositions, mention may be made, for example, of compressed air, carbon dioxide, nitrous oxide, nitrogen, dimethyl ether, liquefiable aliphatic hydrocarbons such as propane, butanes including isobutane, pentane, isopentane, neopentane and mixtures thereof, chlorohydrocarbons and/or fluorohydrocarbons, or mixtures thereof.
Among the chlorohydrocarbons and/or fluorohydrocarbons which may be mentioned are monochlorodifluoromethane, dichlorodifluoromethane, monochlorodifluoroethane, 1,1-difluoroethane and dichlorotetrafluoroethane, as well as mixtures thereof and in particular the mixture of monochlorodifluoro-methane/monochlorodifluoroethane (40/60) as well as the mixture of dichlorodifluoromethane/dichlorotetrafluoro-ethane (60/40).
The proportion of propellant used is not critical, but it determines the density of the foam produced. The higher the proportion of propellant, the lower the foam density. Generally, the foam densities are in the range from about 0.02 g/cm3 to about 0.20 g/cm3 and preferably from about 0.05 g/cm3 to about 0.15 g/cm3.
The proportion of propellant is generally between 1% and 20% by weight relative to the total weight of the aerosol composition, and preferably between 5% and 15%.
The internal pressure in the aerosol container is generally between about 1 and 4 bar (105 to 4xc3x97105 Pa).
Any type of container and valve system for an aerosol foam is suitable for carrying out the invention according to this embodiment.
According to a third embodiment of the compositions according to the invention, they are in the form of dispersion or an emulsion of the oil-in-water or water-in-oil type, and more particularly in the form of a microemulsion or gel.
The aqueous phase is generally present in a proportion of between 60% and 90% for the oil-in-water emulsions and between 30% and 60% for the water-in-oil emulsions, by weight relative to the total weight of the composition.
The fatty phase is generally present in a proportion of between 5% and 25% for the emulsions of oil-in-water type, and between 30% and 50% for the emulsions of water-in-oil type, by weight relative to the total weight of the composition.
The fatty phase consists of at least one cosmetic oil or a mixture of at least one oil and at least one wax, these being of mineral, plant, animal or synthetic origin, as described in patent FR-2 668 927.
Among the emulsifiers which can be used in the compositions in the form of an oil-in-water emulsion, mention may be made, inter alia, of lauryl sulphate, triethanolamine stearate or fatty alcohols such as stearyl alcohol or cetyl alcohol.
Among the emulsifiers which can be used in the compositions in the form of a water-in-oil emulsion, mention may be made, inter alia, of glycerol esters, ethoxylated alcohols, lanolin, lanolin alcohol, cholesterol and various sorbitan oleates.
The emulsifiers are generally present in a proportion of between 1% and 10% by weight relative to the total weight of the composition.
According to this embodiment, the compositions are preferably transparent microemulsions or gels, and contain an excess of emulsifier and at least one mineral oil of low viscosity.
The mineral oils which can be used in the gel compositions contain short carbon-based chains and are present in a proportion of between 15% and 20% by weight relative to the total weight of the composition.
Among the emulsifiers for the compositions in gel form which may be mentioned in particular are polyoxyethylated ether and oleyl alcohol or its phosphonic ester, polyethoxylated lauryl alcohol, polyethoxylated oleyl alcohol, oxyethylated cetyl alcohol and various polyoxythylene glycols of fatty acids.
The compositions in gel form can also contain a coupling agent such as 2-ethylhexane-1,3-diol, a polyhydric alcohol such as sorbitol, a polyethylene glycol, lanolin or lanolin alcohol, as well as preserving agents.
According to a fourth embodiment of the compositions according to the invention, they are in the form of a lotion.
The vehicle for these lotions is either an aqueous solution or an aqueous-alcoholic solution containing, in substantially equal parts, deionized water and an alcohol such as ethanol or isopropanol.
The lotions can also contain at least one substance chosen from an isopropyl ester and a polyalkylene glycol or the oleate thereof.
According to a final embodiment of the compositions according to the invention, they are in the form of a lacquer and more particularly of an aerosol hair lacquer.
The cosmetically acceptable vehicle generally used in the lacquers consists of an alcohol such as ethanol or isopropanol or an aqueous-alcoholic mixture.
The lacquers according to this specific embodiment also contain at least one film-forming resin, at least one plasticizer and a propellant.
The film-forming resins used in the lacquers are well known in the prior art and mention may be made in particular of those described in patent FR-2 684 874, and they are preferably present in a proportion of from 3% to 6% by weight relative to the total weight of the composition.
Among the preferred plasticizers which may be mentioned in particular are glycol ethers, benzyl alcohol, triethyl citrate, 1,3-butylene glycol and propylene carbonate, which are present in a proportion of between X % and Y % by weight relative to the total weight of the composition.
The propellant for the lacquers can be chosen from at least one of the agents listed above for preparing compositions in the form of a mousse.
The lacquers according to this embodiment can also contain other conventional ingredients, such as corrosion inhibitors, softeners, fragrances, silicones, sunscreens, dyes, preserving agents, anti-foaming agents and vitamins.
After introducing the composition or xe2x80x9cfluidxe2x80x9d into a suitable container, the container is fitted with a suitable valve and diffusion system.
Among the valves which can be used, mention may be made in particular of those described in patent FR-2 382 637.
A subject of the present invention is also a repairing care and treatment process for keratin fibres, referred to hereinabove as a xe2x80x9cdirectxe2x80x9d treatment process, this process consisting in applying to the keratin fibres a composition as defined above containing at least one polyamino acid derivative, and in leaving the composition to act on the fibres, optionally followed by rinsing the keratin fibres.
According to one particularly preferred embodiment of the repairing care and treatment process of the keratin fibres, referred to hereinabove as the xe2x80x9cin-situxe2x80x9d treatment process, the polyamino acid derivative of formula (I) is formed xe2x80x9cin situxe2x80x9d, i.e. directly on the keratin fibres which are subjected to the treatment, with the aid of precursors which generate the polyamino acid derivative.
These precursors are, on the one hand, an N-carboxyanhydride of formula (II) and, on the other hand, a nucleophilic compound of formula (III) which, to carry out the treatment, are in the form of a packaging in two parts.
The first part contains at least one N-carboxyanhydride of formula (II) in solid form or diluted in a cosmetically acceptable vehicle, and the second part contains a nucleophilic compound of formula (III), in solid form or diluted in a cosmetically acceptable vehicle.
The cosmetically acceptable vehicle for the N-carboxyanhydride of formula (II) is an organic solvent, water or a mixture thereof. The cosmetically acceptable vehicle for the nucleophilic compound of formula (III) is preferably water.
The xe2x80x9cin-situxe2x80x9d treatment process consists, in a first stage, in applying to the hair, which has optionally been moistened beforehand, the first part of the packaging, after optional dilution using a liquid medium, and then, in a second stage, in applying the second part of the packaging, also after optional dilution, in particular water-based dilution.
According to this process, if so desired, the two parts can be premixed and the solution obtained can be applied directly to the hair.
The hair is then rubbed, which brings about, in aqueous medium, the polycondensation of the precursors as a polyamino acid derivative. The polycondensation is generally complete after a period of about 2 to 30 minutes.
After this period of time, the hair is rinsed and optionally shampooed.